1. Field of the Invention
The present invention relates to a washer, damper thereof, and control method thereof.
2. Discussion of the Related Art
Generally, a washer is an apparatus for washing the laundry using a water current and chemical reaction of a detergent and the like. The washer performs washing, heated washing, rinsing, and dewatering cycles selectively or collectively according to a user's selection.
Washers are mainly categorized into a top-loading type washer and a front-loading type washer according to a laundry-loading system. A tub-rotating type washer and a pulsator type washer belong to the top-loading type washers. And, a drum type washer corresponds to the front-loading type washer.
A tub is provided within a cabinet of the washer to store water therein. A drum or inner tub is rotatably provided within the tub. And, a driving device is provided to the tub to generate a drive force for rotating the drum or inner tub. In this case, the driving device is connected to a washing shaft that is connected to the drum or inner tub.
When the drum or the like is rotated by the driving device, vibration appearing on the driving device, the drum, and the like is transferred to the tub. To absorb the vibration, the tub is supported by dampers and is suspended by suspension springs.
A deceleration device is provided to the washing shaft. Hence, in performing a washing cycle, the drum, which is decelerated by the deceleration device, rotates to wash the laundry. And, the drum rotates at high rotational speed to dewater the laundry in performing a dewatering cycle.
As the drum and the like is excessively shaken in the early stage of the dewatering cycle, excessive vibration is transferred to the tub, which is hereinafter named ‘excessive vibration state’. Subsequently, as a rotational speed of the drum or the like is gradually raised, the vibration transferred to the tub is gradually reduced. Once the drum or the like reaches a normal rotational speed, the vibration transferred to the tub is more considerably reduced than that in the early stage of the dewatering cycle, which is hereinafter named ‘normal vibration state’.
However, the related art washer has the following problems.
First of all, the damper, which provides the same damping force in the excessive or normal vibration state, amplifies the vibration of the drum and the like in the normal vibration state, thereby increasing the noise in performing the dewatering cycle of the washer.
Secondly, the normal vibration state is mostly maintained during the dewatering cycle. Hence, the noise is increased across the dewatering cycle overall.
Thirdly, a time taken to reach the normal vibration state inevitably varies according to an input quantity of the laundry in performing the dewatering cycle. If the normal vibration state is reached more quickly, the amplified noise is sustained for a considerably long time.